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Thread: Double set of galvos

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    Default Double set of galvos

    While watching a video about a very powerful show laser the author mentioned that the galvo mirror mirror size needed to be increased.
    And unfortunately increased mirror means bigger galvos and slower. This all makes sense to me.

    Then I started thinking, would it not be possible to build a laser with a double set of galvos. Mounted in the illustrated arrangement.
    The output beams are offset by 6 mm which makes it possible to divide the scanning workload.

    You could have two laser sources or split the beam which is less efficient.

    Would I be correct to think that this arrangement makes it possible to double the power and double the scanning capability?
    I mean, this is essentially two show lasers that are almost originate from the same point.

    Click image for larger version. 

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    So many questions.
    - Has this been done before?
    - Are there better ways to do this?
    - Can 2 sets of galvos from the same manufacturing batch accurately draw the same graphic with double intensity?


  2. #2
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    Yes, been done. Modern software does combine scan heads well for graphics.

    They need not be as close as they are in your drawing, they may interact from air currents, internal position feedback system, and vibration.

    In the last five years mirror sizes have greatly increased.

    No real need to do that for beam shows, in fact, for beams it looks better if the scan heads are spaced apart. More attractive to the eye that way.

    What we need these days is more angle, which is best done with lenses such as Omniscan and Discoscan, less galvo angle = more speed, and speed is life.

    Steve
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    I should have rented the space under my name for advertising.
    When I still could have...

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    Wide angle I have sorted already. I designed a new mirror called Medusa https://www.youtube.com/watch?v=00KeqktfHzE
    It was a huge success at our Beatline premiere two weeks ago. https://www.youtube.com/watch?v=gFUYn6QV_SI (light canopy at the end)

    Ceiling creeping variants that work without haze here https://www.youtube.com/watch?v=QkVdyl4ETHY

    Click image for larger version. 

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  4. #4
    mixedgas's Avatar
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    I like the haze less version. Neat way to get around the regulatory "low ceiling" problem. It gets cold here in Ohio and a lot of clubs have very low ceilings, making obeying the 3 meter minimum height rule difficult.


    FYI, your working with a "Reflective Axicon" or "Reflective Conic Section
    in optics speak. I like it.

    Steve
    Qui habet Christos, habet Vitam!
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    Thank you Steve,

    It is great to be able to talk to experienced Laserists. I just love well timed lights to a good tune but it's rare. The idea is to do small laser shows at various venues to learn what is required in the real world.
    Then take what I learned and create software and hardware dedicated to create razor sharp low lag beam shows involving multiple devices. This software is already taking shape.

    Quote Originally Posted by mixedgas View Post
    I like the haze less version. Neat way to get around the regulatory "low ceiling" problem. It gets cold here in Ohio and a lot of clubs have very low ceilings, making obeying the 3 meter minimum height rule difficult.


    FYI, your working with a "Reflective Axicon" or "Reflective Conic Section
    in optics speak. I like it.

    Steve
    "Reflective Axicon" I like it. It makes me sound smart.
    Last edited by dinther; 05-16-2024 at 14:46.

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    Quote Originally Posted by dinther View Post
    While watching a video about a very powerful show laser the author mentioned that the galvo mirror mirror size needed to be increased.
    And unfortunately increased mirror means bigger galvos and slower. This all makes sense to me.


    Has anyone considered using beryllium mirrors as a low mass option for scanners? They work great for space telescopes.

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    Lightbulb

    Quote Originally Posted by dchammonds View Post
    Has anyone considered using beryllium mirrors as a low mass option for scanners? They work great for space telescopes.
    Hmm. Google says that Beryllium's density is roughly 1/3 that of Aluminum, and it's stronger as well. Still, the mirrors aren't the major source of weight in a scanning system, so unless we're talking about 2" aperture mirrors or something crazy, I doubt the weight savings would be enough to justify the cost (not to mention the risk of cancer if you break the mirror).

    Carbon fiber would be another option, but again, I don't think the weight savings is going to be enough to matter - unless we're taking about some really huge mirrors.

    If you really want to save weight in a scanning system, remove the position detection hardware that is usually mounted on the other end of the rotor (opposite the mirror). Instead, add a dichro to combine an IR beam with the incoming RGB right before the scanners, and then add a second, larger dichro to pick off the IR immediately after the scanners (and before the aperture glass). Now place 4 stationary IR detectors in a cross configuration (up, down, left, right) a short distance to the side of that second dichro to sense the position of the IR beam. Presto! You now have accurate position feedback signals to send back to the scanner amps, but everything is completely external to the scanner rotors and there are no moving parts.

    Aron Bacs was one of the authors of an AVI patent for this exact technology, but due to a clerical error when they filed the patent application, they didn't include this in their claims declaration, meaning that the concept was basically in the public domain as soon as the patent was published. I'm honestly surprised that this hasn't made it's way into a commercial laser projector yet...

    Adam

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    Quote Originally Posted by buffo View Post
    Hmm. Google says that Beryllium's density is roughly 1/3 that of Aluminum, and it's stronger as well. Still, the mirrors aren't the major source of weight in a scanning system, so unless we're talking about 2" aperture mirrors or something crazy, I doubt the weight savings would be enough to justify the cost (not to mention the risk of cancer if you break the mirror).

    Carbon fiber would be another option, but again, I don't think the weight savings is going to be enough to matter - unless we're taking about some really huge mirrors.

    If you really want to save weight in a scanning system, remove the position detection hardware that is usually mounted on the other end of the rotor (opposite the mirror). Instead, add a dichro to combine an IR beam with the incoming RGB right before the scanners, and then add a second, larger dichro to pick off the IR immediately after the scanners (and before the aperture glass). Now place 4 stationary IR detectors in a cross configuration (up, down, left, right) a short distance to the side of that second dichro to sense the position of the IR beam. Presto! You now have accurate position feedback signals to send back to the scanner amps, but everything is completely external to the scanner rotors and there are no moving parts.

    Aron Bacs was one of the authors of an AVI patent for this exact technology, but due to a clerical error when they filed the patent application, they didn't include this in their claims declaration, meaning that the concept was basically in the public domain as soon as the patent was published. I'm honestly surprised that this hasn't made it's way into a commercial laser projector yet...

    Adam
    Beryllium is common for resonant scanner mirrors (such as CRS 8k and 12k), and for some large galvo mirrors, in the >15mm aperture range, for very high end (expensive) systems.
    Novanta, who acquired Cambridge Technology, has their own Beryllium manufacturing cleanroom facility now
    https://cleanroomtechnology.com/bouy...novanta-204329
    We have some beryllium mirror specimens here, but don't use them for production. We prefer Silicon Carbide for those higher end applications
    Sincerely,
    Ryan Smith
    ScannerMAX Mechanical Engineer
    ryan {at} scannermax.com

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    Quote Originally Posted by buffo View Post

    If you really want to save weight in a scanning system, remove the position detection hardware that is usually mounted on the other end of the rotor (opposite the mirror). Instead, add a dichro to combine an IR beam with the incoming RGB right before the scanners, and then add a second, larger dichro to pick off the IR immediately after the scanners (and before the aperture glass). Now place 4 stationary IR detectors in a cross configuration (up, down, left, right) a short distance to the side of that second dichro to sense the position of the IR beam. Presto! You now have accurate position feedback signals to send back to the scanner amps, but everything is completely external to the scanner rotors and there are no moving parts.
    How about making the mirrors double sided and bouncing the IR off the back and employing 2 IR sensors for each mirror?

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    Quote Originally Posted by rns0504 View Post
    We have some beryllium mirror specimens here, but don't use them for production. We prefer Silicon Carbide for those higher end applications
    Less chance of getting lung cancer with silicon carbide, right?

    Quote Originally Posted by dchammonds View Post
    How about making the mirrors double sided and bouncing the IR off the back and employing 2 IR sensors for each mirror?
    I'm sure that would also work, but it would make the optical path for the IR feedback a lot more complicated. (Seems like the scanner mounting block itself would be in the way.)

    Picking off the IR after the scanners is fairly straightforward (the second dichro only needs to be about 1" square to capture the entire scan field, assuming you mount it very close to the scanners), and the IR detectors can be mounted further to the side so they don't interfere with the scanners or the incoming beam path.

    Adam

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